NASA's DART Mission: How We Tested a Hollywood Idea to Save Earth from Asteroids

In the movie Armageddon (1998), a large asteroid threatens the Earth. Doom is near. However, the American space agency NASA puts together a group of happy oil drillers led by Harry S. Stamper (Bruce Willis). The best solution, at least according to the authors, is to play it safe and drill holes in the rock bumblebee and blast it to pieces with nuclear weapons.

Not so believable, perhaps, but the fact is that NASA conducted a similar, albeit less spectacular, experiment a few years later. Because the Dart space probe was launched in 2022 braka in asteroiden Dimorphos.

– The idea of the accident was to see if, and if so, how, it affected the asteroid and its path. In this way, see if we can protect ourselves from asteroids in the future, says Jan-Erik Wahlund, a researcher at the Institute of Space Physics in Uppsala.

The controlled collision occurred on September 26, 2022. Dart, the Nasa craft that entered the asteroid, weighed almost half a ton and hit at a speed of 22,000 kilometers per hour.

Of course it was it is no coincidence that the researchers chose Dimorphos. On the one hand, it is reasonably large, and on the other hand, it is part of the so-called binary asteroid system. That is, Dimorphos is about 160 meters in diameter. That is, approximately the same size as the asteroids that are considered the greatest threat to Earth. In addition, it orbits the slightly larger asteroid Didymos. In this way, Dimorphos can be compared to a moon whose orbit around Didymos has been precisely calculated.

In September 2022, the Dimophos spacecraft arrived. One thing scientists are now looking for answers to is the mass of the asteroid and how it is structured. Is it solid or does it consist of more loosely assembled parts, called a “debris pile asteroid”?

Photo: NASA

Today, two years later, scientists know that the collision shortened Dimorpho’s orbit by just under a dozen times by 33 minutes. Not bad. The researchers also know that the impact was so powerful that a large clump of material was created after the impact. The plume extended more than 10,000 kilometers into space and lasted for several months. Symbols also show that the crater it created may have been that big that the mass was redistributeduntil Dimorphos was completely deformed. What the researchers do not know, however, is how the impact affected Dimorphos as a whole. That is, how effective the impact was in changing the asteroid’s movement pattern, which was the real point of the experiment.

– To understand that, more detailed knowledge is needed, including the mass of the asteroid. We also want to know what the crater looks like, exactly how Dart hit, what the asteroid is made of, how it is composed and how it moves. But in that case centimeter precision is needed. It cannot be measured from the ground. You have to be there, says Jan-Erik Wahlund.

It is here the Hera spacecraft enters the picture, recently submitted by the European Space Agency ESA. The launch took place on October 7 using a SpaceX Falcon 9 rocket that rose into the sky from the Cape Canaveral Space Force Station in Florida, USA. However, since Dimorphos is between Earth and Mars, it is not expected to arrive until late 2026.

Like a detective, Hera then tries to find out what really happened. To help her, she has, among other things, radar, cameras and infrared imaging technology. The idea is that Hera will circle the two asteroids for six months, while at the same time approaching Dimorphos. In the end, only a few kilometers separate them. After two months, Hera will release two subsatellites, Juventas and Milani, which will also position themselves around the two asteroids. By measuring the distance between the three spacecraft, the researchers will get information on how Dimorpho’s gravity affects them and so they can calculate the size of the asteroid. In the end, both satellites will land on Dimorphos, and Hera will probably land on Didymos.

In this way, the scientists expect to get all the information they need to find out how the explosion affected Dimorphos, and whether it will be possible to protect the Earth from asteroids with sonicating them completely away. But if it tastes good, it costs money. Around four billion Swedish kronor, to be more precise. Whether it’s a lot or a little money probably depends on how big the risk is. That is, the probability that an asteroid will hit the Earth.

– It has been confirmed that it is it happened several times before and it will definitely happen again. We don’t know when, says Jan-Erik Wahlund, who has been working with the Hera project.

The biggest threat, he says, is the “medium” asteroids. That is, asteroids that have a diameter of about a hundred meters.

– The smallest ones burn up in the atmosphere and we have a good understanding for a kilometer. The medium-sized ones, on the other hand, are hard to see and there are thousands of them, says Jan-Erik Wahlund.

In the Tunguska eruption in Siberia in 1908, millions of trees were felled. In 1950, when this photo was taken, the effects were still clearly visible.

Photo: Universal History Archive/UIG/REX

A good example of this is the asteroid that hit Tunguska in Siberia in 1908 and destroyed more than 2,000 square kilometers of forest. The size of this asteroid has been debated, but it is estimated to have “only” a diameter of about 50 meters.

– Then imagine an asteroid twice as big. In that case, the mass will be eight times greater. It will be a huge explosion that could destroy entire cities. You don’t want someone like that in your head. That issue has been resolved. Uppsala would disappear from the map, says Jan-Erik Wahlund.

Why is the effect so great?

– Because it comes at such a fast speed, about 30 kilometers per second. This makes the kinetic effect (energy of motion) absolutely amazing. Far outside the actual impact site, you will be hit by a powerful shock wave that destroys everything.

The meteorite shows that a celestial body can surprise him suddenly he entered in the atmosphere and exploded over Chelyabinsk, Russia in February 2013. Despite being only 17 meters in diameter, the energy released in the explosion was 30 times that of the bomb atomic bomb that exploded over Hiroshima, Japan in 1945.

The meteorite that exploded above Chelyabinsk in Russia is believed to have weighed up to 10,000 tons before it exploded. The photo shows the explosion, which was caught from a car on the highway.

Photo: Nasha gazeta

– The irony was that everyone at the time who was dealing with this kind of thing was busy tracking a completely different asteroid and then this one comes along- out of nowhere and surprised everyone, says Jan-Erik Wahlund.

The hope now, he says, is that Hera will prove what the scientists are hoping for. That Dart managed to change Dimorpho’s path enough for the technique to be useful in the future.

– In that case, this is the first time ever that we have a way to protect ourselves (from asteroids), so why don’t you make sure to do it?

Truth.Meteorite, asteroid or in between

We have always been able to see people meteorsalso known as shooting stars. That is, objects the size of grains of sand that enter the atmosphere at high speed where they burn up.

Objects that shine brighter and longer are said to be slightly larger cars.

If it is big and big enough, it can survive the way down through the atmosphere and be found as strange rocks on the ground. In that case, they are called meteorites. When these move out in space, however, they are called meteoroids.

Some clear line between these and the bigger ones the asteroids it does not exist, however, there are more asteroids than meteoroids. Asteroids are primarily associated with the solid celestial bodies found in the so-called asteroid belt between Mars and Jupiter. The asteroids in this belt can be seen as remnants after the planets were formed.

Source: Swedish Space Agency